With the widespread of large display devices such as liquid crystal televisions, products with higher-value-added have been demanded and thus under development. In particular, a technique to configure a driver circuit such as a scan line driver circuit over the same substrate as a pixel portion, using thin film transistors (TFTs) whose channel regions are made of an amorphous semiconductor has been actively developed because the technique greatly contributes to reduction in cost and improvement in reliability.
Further, reduction in power consumption of the display device is a large object. Patent Document 1 discloses an image display device having a partial display function, which is equipped with an output control block which controls an output of an ON signal to a scan signal line such that display scan signals are output in a batch to a plurality of scan signal lines for a non-display region, in response to a control signal for switching the output of an ON signal to a scan signal line from sequential output to batch output.